diff --git a/lib/polymorphic_embed/html/helpers.ex b/lib/polymorphic_embed/html/helpers.ex
index 7822d46..285f59f 100644
--- a/lib/polymorphic_embed/html/helpers.ex
+++ b/lib/polymorphic_embed/html/helpers.ex
@@ -49,7 +49,7 @@ if Code.ensure_loaded?(Phoenix.HTML) && Code.ensure_loaded?(Phoenix.HTML.Form) d
       form.source.data.__struct__
     end
 
-    def to_form(%{action: parent_action} = source_changeset, form, field, options) do
+    def to_form(source_changeset, %{action: parent_action} = form, field, options) do
       id = to_string(form.id <> "_#{field}")
       name = to_string(form.name <> "[#{field}]")
 
@@ -57,36 +57,60 @@ if Code.ensure_loaded?(Phoenix.HTML) && Code.ensure_loaded?(Phoenix.HTML.Form) d
 
       struct = Ecto.Changeset.apply_changes(source_changeset)
 
-      list_data =
-        case Map.get(struct, field) do
-          nil ->
-            type = Keyword.get(options, :polymorphic_type, get_polymorphic_type(form, field))
-            module = PolymorphicEmbed.get_polymorphic_module(struct.__struct__, field, type)
-            if module, do: [struct(module)], else: []
+      Map.get(source_changeset.changes, field)
+      |> case do
+        nil ->
+          case Map.get(struct, field) do
+            nil ->
+              type = Keyword.get(options, :polymorphic_type, get_polymorphic_type(form, field))
+              module = PolymorphicEmbed.get_polymorphic_module(struct.__struct__, field, type)
+              if module, do: [struct(module)], else: []
 
-          data ->
-            List.wrap(data)
-        end
+            data ->
+              List.wrap(data)
+          end
 
-      list_data
+        data when is_list(data) ->
+          data
+
+        data ->
+          List.wrap(data)
+      end
       |> Enum.with_index()
-      |> Enum.map(fn {data, i} ->
-        params = Enum.at(params, i) || %{}
+      |> Enum.map(fn
+        {%Ecto.Changeset{} = changeset, i} ->
+          params = changeset.params || %{}
+          errors = get_errors(changeset)
 
-        changeset =
-          data
-          |> Ecto.Changeset.change()
-          |> apply_action(parent_action)
+          %{changeset: changeset, params: params, errors: errors, index: i}
 
-        errors = get_errors(changeset)
+        {data, i} ->
+          params = Enum.at(params, i) || %{}
 
-        changeset = %Ecto.Changeset{
-          changeset
-          | action: parent_action,
-            params: params,
-            errors: errors,
-            valid?: errors == []
-        }
+          changeset =
+            data
+            |> Ecto.Changeset.change()
+            |> apply_action(parent_action)
+
+          errors = get_errors(changeset)
+
+          changeset = %{
+            changeset
+            | action: parent_action,
+              params: params,
+              errors: errors,
+              valid?: errors == []
+          }
+
+          %{changeset: changeset, params: params, errors: errors, index: i}
+      end)
+      |> Enum.map(fn prepared_data ->
+        %{
+          changeset: changeset,
+          params: params,
+          errors: errors,
+          index: i
+        } = prepared_data
 
         %schema{} = source_changeset.data
 
@@ -106,7 +130,8 @@ if Code.ensure_loaded?(Phoenix.HTML) && Code.ensure_loaded?(Phoenix.HTML.Form) d
           name: if(array?, do: name <> "[" <> index_string <> "]", else: name),
           index: if(array?, do: i),
           errors: errors,
-          data: data,
+          data: changeset.data,
+          action: parent_action,
           params: params,
           hidden: [{type_field_name, to_string(type)}],
           options: options
diff --git a/test/polymorphic_embed_test.exs b/test/polymorphic_embed_test.exs
index 7dced00..01d3d44 100644
--- a/test/polymorphic_embed_test.exs
+++ b/test/polymorphic_embed_test.exs
@@ -2704,15 +2704,26 @@ defmodule PolymorphicEmbedTest do
     for generator <- @generators do
       reminder_module = get_module(Reminder, generator)
 
-      attrs = %{
-        date: ~U[2020-05-28 02:57:19Z],
-        text: "This is an Email reminder",
-        channel: %{
-          address: "a",
-          valid: true,
-          confirmed: true
-        }
-      }
+      attrs =
+        if polymorphic?(generator) do
+          %{
+            date: ~U[2020-05-28 02:57:19Z],
+            text: "This is an Email reminder",
+            channel: %{
+              address: "a",
+              valid: true,
+              confirmed: true
+            }
+          }
+        else
+          %{
+            number: ~U[2020-05-28 02:57:19Z],
+            text: "This is a non polymorphic reminder",
+            channel: %{
+              number: "a"
+            }
+          }
+        end
 
       changeset =
         struct(reminder_module)
@@ -2721,8 +2732,19 @@ defmodule PolymorphicEmbedTest do
       contents =
         safe_inputs_for(changeset, :channel, generator, fn f ->
           assert f.impl == Phoenix.HTML.FormData.Ecto.Changeset
-          assert f.errors == []
-          text_input(f, :address)
+
+          if polymorphic?(generator) do
+            assert f.errors == [
+                     {:address,
+                      {"should be at least %{count} character(s)",
+                       [count: 3, validation: :length, kind: :min, type: :string]}}
+                   ]
+
+            text_input(f, :address)
+          else
+            assert f.errors == []
+            text_input(f, :number)
+          end
         end)
 
       expected_contents =
@@ -2732,7 +2754,7 @@ defmodule PolymorphicEmbedTest do
           <input id="reminder_channel_address" name="reminder[channel][address]" type="text" value="a">
           """,
           else: ~s"""
-          <input id="reminder_channel_address" name="reminder[channel][address]" type="text" value="a">
+          <input id="reminder_channel_number" name="reminder[channel][number]" type="text" value="a">
           """
         )
 
@@ -2745,7 +2767,12 @@ defmodule PolymorphicEmbedTest do
           generator,
           fn f ->
             assert f.impl == Phoenix.HTML.FormData.Ecto.Changeset
-            text_input(f, :address)
+
+            if polymorphic?(generator) do
+              text_input(f, :address)
+            else
+              text_input(f, :number)
+            end
           end
         )
 
@@ -2756,7 +2783,7 @@ defmodule PolymorphicEmbedTest do
           <input id="reminder_channel_address" name="reminder[channel][address]" type="text" value="a">
           """,
           else: ~s"""
-          <input id="reminder_channel_address" name="reminder[channel][address]" type="text" value="a">
+          <input id="reminder_channel_number" name="reminder[channel][number]" type="text" value="a">
           """
         )
 
@@ -3204,6 +3231,97 @@ defmodule PolymorphicEmbedTest do
     end)
   end
 
+  test "form with improved param handling for different param types" do
+    reminder_module = get_module(Reminder, :polymorphic)
+
+    # Test with nil params - when contexts is empty, safe_inputs_for returns empty string
+    changeset_nil_params =
+      struct(reminder_module)
+      |> reminder_module.changeset(%{text: "Test reminder", contexts: []})
+      |> Map.put(:params, %{"contexts" => nil})
+      |> Map.put(:action, :insert)
+
+    safe_form_for(changeset_nil_params, fn _f ->
+      safe_inputs_for(changeset_nil_params, :contexts, :polymorphic, fn f ->
+        assert f.impl == Phoenix.HTML.FormData.Ecto.Changeset
+        assert f.errors == []
+        assert f.params == %{}
+
+        1
+      end)
+
+      1
+    end)
+
+    # Test with list params - need to add some contexts to the data
+    changeset_list_params =
+      struct(reminder_module)
+      |> reminder_module.changeset(%{
+        text: "Test reminder",
+        contexts: [
+          %{__type__: "device", ref: "123", type: "cellphone"},
+          %{__type__: "location", address: "456 Main St"}
+        ]
+      })
+      |> Map.put(:params, %{"contexts" => [%{"ref" => "123"}, %{"address" => "456 Main St"}]})
+      |> Map.put(:action, :insert)
+
+    safe_form_for(changeset_list_params, fn _f ->
+      safe_inputs_for(changeset_list_params, :contexts, :polymorphic, fn f ->
+        assert f.impl == Phoenix.HTML.FormData.Ecto.Changeset
+        assert f.errors == []
+        # First context should have params from index 0
+        if f.index == 0 do
+          assert f.params == %{"ref" => "123"}
+        end
+
+        # Second context should have params from index 1
+        if f.index == 1 do
+          assert f.params == %{"address" => "456 Main St"}
+        end
+
+        1
+      end)
+
+      1
+    end)
+
+    # Test with map params - need to add some contexts to the data
+    changeset_map_params =
+      struct(reminder_module)
+      |> reminder_module.changeset(%{
+        text: "Test reminder",
+        contexts: [
+          %{__type__: "device", ref: "789", type: "cellphone"},
+          %{__type__: "location", address: "012 Oak Ave"}
+        ]
+      })
+      |> Map.put(:params, %{
+        "contexts" => %{"0" => %{"ref" => "789"}, "1" => %{"address" => "012 Oak Ave"}}
+      })
+      |> Map.put(:action, :insert)
+
+    safe_form_for(changeset_map_params, fn _f ->
+      safe_inputs_for(changeset_map_params, :contexts, :polymorphic, fn f ->
+        assert f.impl == Phoenix.HTML.FormData.Ecto.Changeset
+        assert f.errors == []
+        # First context should have params from key "0"
+        if f.index == 0 do
+          assert f.params == %{"ref" => "789"}
+        end
+
+        # Second context should have params from key "1"
+        if f.index == 1 do
+          assert f.params == %{"address" => "012 Oak Ave"}
+        end
+
+        1
+      end)
+
+      1
+    end)
+  end
+
   describe "get_polymorphic_type/3" do
     test "returns the type for a module" do
       assert PolymorphicEmbed.get_polymorphic_type(